The effectiveness of a heat sink is a function of the thermal conductivity of the heat sink material, so materials of high thermal conductivity are preferred for use as heat sinks. Diamond has the highest thermal conductivity of any known material. Silver, copper, and aluminum are among the best cheaper alternative heat sink materials but, in addition to having much lower thermal conductivities than diamond, they are much heavier than diamond, and are not electrical insulators.
Synthetic diamond, such as polycrystalline diamond film made by chemical vapor deposition ("CVD"), has a thermal conductivity which can approach that of natural diamond, and has been used as a heat sink material, but is expensive.
The thermal conductivity of CVD synthetic diamond varies generally in proportion to the quality thereof which, other things being equal, is generally an inverse function of the rate at which it was deposited. Synthetic diamond produced at a relatively high deposition rate will generally have a substantially lower thermal conductivity than synthetic diamond deposited at a relatively low deposition rate. This is because the synthetic diamond deposited at a higher deposition rate tends to have more structural defects which adversely affect thermal conduction. Therefore, ideally, synthetic diamond to be used as a heat sink material would be synthesized at a relatively low deposition rate in order to have the highest attainable thermal conductivity. However, this approach is problematic in that diamond synthesized at a low deposition rate will be substantially more expensive than its lower thermal conductivity counterpart synthesized at a higher deposition rate, owing to the increased time of use of expensive deposition equipment, increased power consumption, and increased feedstock material use.
It is among the objects of the present invention to maximize the effective thermal conductivity of diamond synthesized for use in thermal management of electronic components and circuits, without undue increase in expense of synthesizing the diamond material for such application.